Polymer Science, Series B最新文献

Nitrogen-oxygen co-doped porous carbon microspheres were synthesized through hydrothermal and carbonization processes using polyimide (PI) as the carbon precursor and a nitrogen-oxygen source. ZIF-8 was also used as the template. When the carbonization temperature reached 800°C, the porous carbon microspheres displayed a unique 3D sea urchin-like morphology, a high specific surface area (782.3 m²/g), and good nitrogen and oxygen doping contents (6.62 and 11.92 at %, respectively). Electrochemical testing showed that when the scanning rate was 0.5 A/g, the material achieved a specific capacitance of 330.5 F/g, and the capacitance retention rate of the electrode material was 73.5% when the current density reached 10 A/g. Furthermore, the symmetrical supercapacitor assembled with this electrode had an operating voltage window that extended to 1.8 V and provided an energy density of 20.5 W h/kg at a power density of 400 W/kg. This method of preparing high performance nitrogen-oxygen co-doped carbon electrode materials provides an idea for the application of insulating polymers in the field of energy storage.

Novel catalytic systems based on complexes of copper(II) bromide with polydentate nitrogen-containing ligands, tris[(2-pyridyl)methyl]amine and tris[(2-dimethylamino)ethyl]amine, and salts of organic acids (Rochelle salt, sodium oxalate, sodium lactate, and sodium pyruvate) acting as catalyst regenerating agents have been developed for the radical polymerization of acrylonitrile. It has been shown that the polymerization of acrylonitrile carried out in the presence of these systems and halogen-containing initiators occurs by the atom transfer mechanism, affording polymers with target molecular weight values. Effect of the nature of reducing agent and initiator on the process of polymerization and the degree of control over molecular weight characteristics of the resulting samples has been studied. It has been found that Rochelle salt and sodium oxalate are the most efficient reducing agents allowing for a high rate of polymerization while maintaining control over the process.

Urea formaldehyde (UF), melamine formaldehyde (MF) and melamine urea formaldehyde (MUF) resins are the most common thermosetting resins. The most obvious advantage of MUF resin over urea formaldehyde resin is that it has much higher resistance to water. MUF resins, synthesized by condensing precursors such as melamine, urea and formaldehyde, have good flame-retardant properties as they release nitrogen gas when burning. Improving the mechanical, thermal and barrier properties of MF and MUF resins by adding various nanoparticles has become very interesting. One of the promising areas of use of MUF resin is their use as insulation foams. In particular, organo clay MUF nanocomposite foams have the potential to offer significant advantages such as improved mechanical and thermal properties as well as reduced water sensitivity. This study aims to prepare and characterize melamine urea formaldehyde organo-clay nanocomposite foams, as well as to examine their properties such as thermal insulation and compressive strength, by using the microwave irradiation technique together with thermal treatment, which can offer advantages such as high reaction rate, yield and purity, and short curing time. Characterization of virgin polymer and melamine formaldehyde organo clay nanocomposite foams prepared by in situ polymerization method, was made using XRD, FTIR, SEM, and HRTEM methods. Spectroscopic and microscopic analyzes showed that the organo-clay platelets exhibited an exfoliated distribution in the melamine-urea-formaldehyde polymer matrix, which did not change with increasing clay content. Although the highest compressive strength values were obtained in virgin MUF foam (0.44 MPa), the values, which partially decreased in nanocomposites, increased with increasing clay ratio and reached 0.38 MPa in the nanocomposite prepared with the highest clay ratio of 0.45 wt %. On the other hand, thermal conductivity coefficients decreased regularly with increasing clay content. Thus, it was concluded that the nanocomposite containing 0.45 organo clay by weight had optimal properties in terms of both strength and thermal insulation.

A new approach to the synthesis of polyrotaxanes from the polyethylenimine‒block‒poly(ethylene glycol)‒block‒polyethylenimine copolymer and alpha-cyclodextrin has been proposed. It has been shown that the acylation of free amino groups of polypseudorotaxane effectively blocks decomposition of the complex in solution. The structure of the synthesized copolymers has been studied in detail by ¹Н and ¹³С NMR spectroscopy, IR analysis, and GPC. It is assumed that the observed abnormally high optical activity of the resulting rotaxanes is probably associated with the formation of chiral helical supramolecular structures.

Copolymers were synthesized from acrylate monomers and ladder-shaped polysilsesquioxanes (LPSQ) using free radical polymerization, and the copolymers were coated on polyethylene terephthalate (PET) films by the lift-off impregnation method. The nanosized SiO₂ sols with different particle sizes were prepared by sol-gel method, and then the nanosized SiO₂ sols were coated on the surface modified PET film to construct a moth-eye-like anti-reflection coating by using the layer-by-layer self-assembly method. The structure and composition of LPSQ and modified acrylic resin copolymer were characterized by infrared spectroscopy and X-ray diffraction, and the transmittance/haze tester and UV spectrophotometer were used to test the performance of the anti-reflection coating, which could reach 94.0% compared with 89.2% of the matrix pure PET film. Thermogravimetric analysis showed that the thermal decomposition temperature of the LPSQ-modified copolymer material was higher than that of the pure acrylate copolymer.

In this study, polythiophene (PTh) was synthesized by polymerization of thiophene (Th) using the chemical oxidative polymerization method. 4-Amino-1-naphthalenesulfonic acid (Sa) was polymerized through enzymatic polymerization method. After that, conductive polymer mixture was prepared by mixing PTh and PSa. To increase the conductivity of PTh, ionic and nonionic surfactants were used such as sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB) and Triton X-100 (Tri-X). The prepared polymer mixtures doped with surfactants were analized by SEM, FTIR spectroscopy, UV–Vis spectroscopy. HOMO-LUMO band gaps, electrochemical properties and electrical conductivity were also analyzed. As a result, it was observed that the conductivity, electrochemical and optical properties of [PTh/PSa] _CTAB were better than those of [PTh/PSa]_SDS and [PTh/PSa]_Tri-X.

In this paper, by means of forming alternately broad-narrow band gap unit in the backbones of polymers to regulate polymer light-emitting color, a series of ethynyl-linked alternating aromatic ring oligomers (P1, P2, P3 and P4) were designed and prepared by Sonogashira coupling polycondensation. These polymers have M_w 35524–12852 in moderate yields (35–67%). The influence of this kind of polymer’s structures on the optical properties was studied in detail with ¹H NMR,¹³C NMR, FTIR, UV, FL, CV, TGA, and fluorescence lifetime test. The results showed that these polymers exhibited good solubility, high thermal stabilities, high oxidative stability, stable optical properties and emitted variously colored fluorescence in moderate quantum yields (28–61%) due to their different energy gap. The fluorescence lifetimes of the polymers P1, P2, P3, and P4 were 0.8974, 1.695, 1.728, and 0.5929 ns, respectively. And the values of lifetime decrease with increasing solvent polarity. The effective light-emitting color regulation of poly(aryleneethynylene)s was realized by Gaussian calculation and experiment results.

The curing kinetics of the epoxy resin/nano rare earth oxides system were studied by non-isothermal differential scanning calorimetry. Curing reaction occurred with DSC thermal analyzers at heating rates of 5, 10, 15, and 20 K/min, respectively. Data on enthalpy changes during heating were collected. The kinetic parameters and curing temperature of the curing reaction of the epoxy resin/ nano rare earth oxides system were calculated by Kissinger–Ozawa, Crane method and T-β extrapolation method. The results showed that the rare earth compounds reduced the activation energy of the epoxy resin curing reaction, but did not change the curing mechanism of the epoxy resin. Studies on the influence of sample fracture morphology showed that the introduction of nano rare earth compounds plays an important role in improving the tensile properties of nanocomposites. When the 1% weight component of nano Gd₂O₃ was added to the composite, the tensile strength of the composite increased by 65.18%, the flexural strength and modulus increased by 57.92 and 70.04%, respectively, and the glass transition temperature increased by 17.55°C.

In this paper, TiO₂ particles submicron were prepared by sol-gel method and modified with 3-aminopropyl triethoxysilane (KH550) after coating SiO₂ on its surface. Subsequently, combined with the breath figure method (BF), slippery liquid-infused porous surfaces (SLIPS) of polyimide composites were prepared by a two-step method using TiO₂/SiO₂ particles, amino terminated polysiloxanes (APT-PDMS), 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) and 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) as the raw materials. The compositions and properties of the composites were characterized by infrared spectroscopy, nuclear magnetic resonance and thermal weight loss, respectively. The apparent morphology of the porous membrane was observed by scanning electron microscopy, and the hydrophobic properties of the porous membrane were investigated before and after the infilling of the silicone oil by contact angle tester. The results show that the hydrophobicity of the porous substrate prepared when the content of TiO₂/SiO₂ particles is 15% and the concentration of composite material is 20 mg/mL is the best, and the sliding angle of the oil-filled SLIPS is 2° at the minimum. The SLIPS owns good stability, self-cleaning, and anti-freezing properties and so on.

The radical polymerization of methyl methacrylate by the atom transfer radical polymerization (ATRP) mechanism under the action of systems based on ruthenium(II) and ruthenium(III) carborane complexes containing chelate P‒O‒P ligands of various structures has been studied. It has been shown that systems based on these metal complexes, carbon tetrachloride, and isopropylamine as a reducing agent are capable of initiating the radical polymerization of methyl methacrylate. The most effective among those studied are systems based on ruthenacarboranes containing 9,9-dimethyl-4,5-bis-(diphenylphosphino)xanthene as a ligand. These compounds are capable of carrying out the process in a controlled manner, as evidenced by a linear increase in the molecular weight of the polymer and a decrease in dispersity values with increasing conversion. The controlled process according to the ATRP mechanism is confirmed by the presence of chlorine atoms at the ends of the polymer chains, as it has been detected by MALDI mass spectrometry. It has been shown that the possibility of coordination of the ruthenium atom with the oxygen atom of the ligand reduces the rate of the polymerization process and the degree of control over it.